The study is a continuation of work in progress. The effects of sympatheticomimetic amines without and with alpha and beta blocking agents and after pretreatment with atropine and cooling were studied in the chick embryo of 3.5 days incubation age. In addition, the effects of scopolamine, acetylcholine, physostigmine, tetramethyl ammonium hydroxide, dimethylphenylpiperazine and the ganglionic blocking agents, pentolinium and Arfonad were also studied in embryos of 6 days incubation age. The response to sympathomimetic amines without and wth alpha and beta blockade in the 3.5 day old embryo have been described previously. It is known that morphologically nervous elements can be demonstrated to be present near and in some portions of the heart (cardiovascular system) in the 6 day old embryo. The studies employing ganglionic stimulating and blocking agents demonstrated that the nervous elements apparently are functioning as well. Both after administration of TMA and DMPP there is a transient rise in heart rate and arterial pressure, effects which can be completely abolished after pretreatment of the embryo with pentolinium or Arfonad.